Epinephrine (INN) (IPA: [ˌɛpɪˈnɛfrən]) or adrenaline (European Pharmacopoeia and British Approved Name|BAN) (IPA: [əˈdrɛnələn]), sometimes spelled "epinephrin" or "adrenalin" respectively, is a hormone. It is a catecholamine, a sympathomimetic monoamine derived from the amino acidsphenylalanine and tyrosine. The Latin roots ad-+renes and the Greek roots epi-+nephros both literally mean "on/to the kidney" (referring to the adrenal gland, which sits atop the kidneys and secretes epinephrine). Epinephrine is sometimes shortened to epi or to EP in medical jargon.

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In May 1886, William Bates reported the discovery of a substance produced by the adrenal gland in the New York Medical Journal. Epinephrine was isolated and identified in 1895 by Napoleon Cybulski, a Polish physiologist. The discovery was repeated in 1897 by John Jacob Abel.[1]

Jokichi Takamine, a Japanese chemist, independently discovered the same hormone in 1900.[2][3]

Epinephrine is a "fight or flight" hormone which is released from the adrenal glands when danger threatens. When secreted into the bloodstream, it rapidly prepares the body for action in emergency situations. The hormone boosts the supply of oxygen and glucose to the brain and muscles, while suppressing other non-emergency bodily processes (digestion in particular).

Epinephrine is used as a drug to treat cardiac arrest and other cardiac dysrhythmias resulting in diminished or absent cardiac output; its action is to increase peripheral resistance via alpha-stimulatedvasoconstriction, so that blood is shunted to the body's core. This beneficial action comes with a significant negative consequence—increased cardiac irritability—which may lead to additional complications immediately following an otherwise successful resuscitation. Alternatives to this treatment include vasopressin, a powerful antidiuretic which also increases peripheral vascular resistance leading to blood shunting via vasoconstriction, but without the attendant increase in myocardial irritability.

For norepinephrine to be acted upon by PNMT in the cytosol, it must first be shipped out of granules of the chromaffin cells. This may occur via the catecholamine-H+ exchanger VMAT1. VMAT1 is also responsible for transporting newly synthesized epinephrine from the cytosol back into chromaffin granules in preparation for release.

Thus, depending on the patient, administration of epinephrine may raise or lower blood pressure, depending whether or not the net increase or decrease in peripheral resistance can balance the positive inotropic and chronotropic effects of epinephrine on the heart, effects which respectively increase the contractility and rate of the heart.

Although widely referred to as adrenaline outside of the US, and the lay public worldwide, the USAN and INN for this chemical is epinephrine because adrenaline bore too much similarity to the Parke, Davis & Co trademark adrenalin (without the "e") which was registered in the US. The BAN and EP term for this chemical is adrenaline, and is indeed now one of the few differences between the INN and BAN systems of names.

Amongst US health professionals, the term epinephrine is used over adrenaline. However, it should be noted that universally, pharmaceuticals that mimic the effects of epinephrine are called adrenergics, and receptors for epinephrine are called adrenoceptors.